When he was young, he built forts out of cardboard and an abundance of tape. But the amount of tape necessary to construct his small dwellings seemed inefficient. He thought, isn’t there a better way?

It was out of this childhood idea an unlikely business venture grew.

Klein, now 15 and a Fairfield Warde High School freshman, and his 18-year-old sister Ayana, a Warde senior, last year launched 3Duxdesign, creating and selling a product that would answer Ethan’s early query.

“They’re 3D printed connectors that are made to fit on any one-ply cardboard. We have six different shapes that help kids learn about basic geometry,” Ethan said.

On their site, the Kleins offer three separate sets of connectors, a cardboard set and architectural sets that allow users to create different models, such as “The Rocketship,” “The Sailboat” or the “Modhaus Architectural Set.” The siblings view them as tools to be used primarily in a STEAM (science, technology, engineering, art and math) educational context.

The products recently won the Kleins the CTNext Entrepreneur Innovation Award, a $10,000 grant given to the state’s most promising startups. The pair sent a written application to CTNext, and were picked to compete against eight other finalists in April at Westport’s Maker Faire. The Kleins made a pitch in front of a six-member panel.

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“We had five minutes to describe our product, and then they had three minutes to ask us questions. So it’s sort of like ‘Shark Tank,’ like a mini version of that,” Ayana said.

Of the eight finalists, 3Duxdesign was one of four to be awarded a grant, which the siblings will use toward upgrading equipment and purchasing other materials.

Building a business

Before opening the business, the Kleins had access to a 3D printer, thanks to their parents, local doctors who own a furniture store. Their parents’ work gave Ayana and Ethan an early view into the business world.

“Both of my parents are doctors, so we had no business in our background. But then when they opened up the furniture company, we watched them go through the process and helped them face all their setbacks and how they worked through them,” Ayana said.

Ayana had considerable experience in engineering. Early in her high school career, Ayana was enrolled in an architecture program at Columbia University, where she said she learned about the design process. She shadowed at an industrial design and engineering firm last summer, as well.

Those experiences have helped the Kleins’ fledgling business thrive. In a little over six months, their products are in 28 schools — mostly in the Hartford area — eight local stores and have sold more than 1,700 units. The products are packaged and distributed by the Kleins and their parents in the factory space they purchased on Barnum Avenue in Bridgeport, where they spend several hours a week, often after school, working.

They hope to expand production by outsourcing the creation of the connectors, rather than the current method of running 3D printers in their home almost 24/7 to keep up with orders. They recently upgraded their cardboard cutter to a faster model.

“Instead of taking about a half hour to cut three kits’ worth of cardboard, it takes about 30 seconds,” Ethan said.

The Kleins have hopes of adding sales staff to their operation and getting their products into more wholesale stores.

“We’d like to get into more schools. Twenty-eight is a pretty good start for only being open six months. We’re trying to branch out to different states,” Ethan said. “We’re going to try to expand our boundaries more.”